Basically, the disposable hypodermic syringe embodied in this invention comprises a cylindrical glass cartridge barrel which is open at both its forward and its rearward ends. The forward end has a necked down portion terminating in an annular flange having an outer diameter greater than that of the necked down portion and generally less than that of the cylindrical barrel. A stopper closes off the opening in the forward end of the cylindrical barrel formed by the annular flange.
A plastic needle hub is fitted onto the necked down end of the cylindrical barrel. The plastic hub comprises a cylindrical body having a forward end mounting a needle. The diameter of the inner surface of the hub cylindrical body is sized to fit snugly over the annular flange of the cylindrical barrel and terminates in an inwardly directed annular locking lip having an inner diameter less than the outer diameter of the annular flange of the cylindrical barrel and adapted to snugly engage the backside of the annular flange after the hub cylindrical body is snapped onto and over the annular flange. It should be noted that the plastic hub is made from a material which will give slightly and thus provide the snap-on qualities desired in the hub.
The rearward portion of the cylindrical barrel is provided with a sealing piston to thereby provide a sealed chamber between the stopper in the forward end and the piston in the rearward end. Suitable operating means are associated with the piston to assist in the injection procedure.
The industry for a number of reasons has been leaning toward the use of plastic hubs particularly for use in disposable units. As might be expected plastic has brought new problems into the field. First of all, the sterilization problem appears. How much heat can the plastic stand and just what kind of heat may it be. Secondly, how do you attach the needle to the plastic hub and thirdly, how do you attach the hub to the cartridge tube or body.
In this particular plastic hub the material used is polycarbonate. It will withstand the requisite heating for sterilization purposes and the needle may be secured thereto using UV curable adhesives. It is capable of slight giving i.e., elastic enough to allow and provide the desired snap-on quality for the hub body onto the annular flange on the cylindrical barrel.
The use of plastic for making cannula hubs is well known in the prior art. For example, Keller U.S. Pat. No. 3,372,697 discloses plastic hubs wherein the materials may be either polypropylene or polycarbonate. In a more recent development, U.S. Pat. No. 4,240,423 to Akhaui discloses a transparent polycarbonate material wherein the deflection temperature is no lower than 270.degree. F. and is therefore suitable for use where autoclave temperature may range from 240.degree. to 260.degree. F. It is further stated that the cannula may be secured to the hub by an expoxy-type adhesive that will withstand steam sterilization temperatures of 240.degree. to 260.degree. F.
With regard to the securing of plastic hubs to the cartridge tube the patent to Keller U.S. Pat. No. 3,372,697 is again very interesting. In FIG. 8 the hub skirt 76 is deformed at 82 by a spinning operation to secure the hub to the enlarged head of the cartridge. It should be noted that the inner end of the cannula 80 extends inwardly beyond the stopper 75 so that the medicament will never come in contact with the cannula hub. In the embodiment illustrated in FIG. 5 a snap-on arrangement is provided wherein flange 62 of the hub body 60 overlys the rear face of cartridge head 52. Here it must be observed that the body 60 is directly bonded to the cartridge head 52 by means of bonding material 56. Again the medicament cannot come in contact with the hub at anytime.
Yet another way of securing a needle hub to the cartridge tube is illustrated in FIG. 1 of Sarnoff U.S. Pat. No. 3,421,155 wherein needle holder 20 is clamped to the vial by spinning an aluminum collar 28 over the shoulder of a terminal portion 30 of the vial and over an annular flange 32 integral with the holder.
The use of shrinkable plastic material as a sealing means is well known in the prior art for specific purposes. For example, Steenhuisen et al U.S. Pat. No. 4,475,903 is directed to a disposable syringe comprising a barrel which has on its tooled end a needle connection with an injection needle and needle guard. A sealing member is provided for the needle guard and consists of a sleeve of shrinkable plastic material. This sleeve is shrunk on one side around the needle connection and/or around the barrel or a front part of the barrel and, on the other side around a part of the needle guard adjoining the needle connection. See FIG. 2 of the drawings for such an arrangement. It should be noted that the wrap is provided with perforations 19 to make it easier to remove the needle guard by breaking the seal at the weakened area. See FIG. 3. It is stated in the specification that although an unperforated sleeve can contribute to maintenance of the sterility of the syringe, the perforated embodiment is preferred. It should be further noted, as shown in FIG. 4, the shrink wrap may extend over the entire syringe including the barrel. Apparently having the wrap around the barrel protects the barrel from some type of breakage.
With the foregoing in mind it is an object of this invention to provide a disposable hypodermic syringe having a cylindrical glass barrel open at both its front and rearward ends with the forward tooled end terminating in an annular flange, a stopper closing the tooled end of the barrel, and a plastic needle hub having a cylindrical body adapted to snugly fit over the annular flange and with a tightly engaging wrap firmly engaging both the hub body and the adjacent portion of the glass barrel to provide a two-fold function namely to enhance the seal formed between the hub body and the annular flange and to assit in retaining the hub body firmly on the annular flange.
It is another object of this invention to make the wrap set forth in the preceding object with a heat shrinkable material.
It is yet another object of this invention to provide the hub body with several slits to increase the resilency of the body to aid in assembly onto the annular flange.
The foregoing and additional objects and advantages will become more apparent when taken in conjunction with the following detailed description and drawings covering a preferred embodiment of this invention.